Core/shell copolymer dispersion whose shell comprises hydrolyzable organosilicon comonomers

ABSTRACT

The invention relates to core/shell copolymer dispersions whose shell comprises hydrolyzable organosilicon comonomers, the shell consisting of a copolymer comprising, 
     a) from 70 to 95% by weight of acrylic and/or methacrylic C 1  to C 10  alkyl esters of which from 20 to 80% by weight, based on the overall weight of a), have a water-solubility of not more than 2 g/l and from 80 to 20% by weight, based on the overall weight of a), have a water-solubility of at least 10 g/l, 
     b) from 5 to 25% by weight of one or more ethylenically unsaturated, functional and water-soluble monomers including a proportion of from 25 to 100% by weight, based on the overall weight of b), of unsaturated carboxylic acids, and 
     c) from 0.01 to 10% by weight of one or more olefinically unsaturated, hydrolyzable silicon compounds of the general formula R 1  --Si(OR 2 ) 3 , 
     and whose core, making up a proportion of from 75 to 98% by weight of the overall weight of the core/shell copolymer, consists of a polymer comprising 
     d) one or more comonomers from the group consisting of vinyl esters, acrylic and/or methacrylic esters, vinyl chloride, vinylaromatic compounds and ethylene.

BACKGROUND OF THE INVENTION

1) Field of the Invention

The invention relates to core/shell copolymer dispersions whose shellcomprises hydrolyzable organosilicon comonomers, to processes for theirpreparation, and to their use as binders for paints, plasters and tileadhesives having good water resistance.

2) Background Art

In order to improve wet adhesion in their application as coatingcompositions, comonomers comprising silanol groups are incorporated bycopolymerization into the copolymers of polymer dispersions. Inaccordance with the prevailing teaching, binders of high quality interms of their water resistance are obtained by polymerizing ahydrolyzable organosilicon compound together with the major proportionof the monomers employed. The prior art describes a range of methods forachieving this.

U.S. Pat. No. 3,814,716 describes polymer dispersions based on vinylacetate, acrylic ester, maleic and/or fumaric ester with 0.5-5% of acopolymerizable silane. The silane is dissolved in the entirety of themonomers employed, and the monomers--including the silane--are dividedinto an initial charge and a portion which is metered in slowly in thecourse of polymerization.

DE-C-21 48 457 (GB-A-1 407 827) discloses the use of dispersionscontaining silanol groups as binders of architectural coatingcompositions. Polymers of vinyl esters, acrylic esters orbutadiene/styrene copolymers are used, into which silanol groups areincorporated by copolymerization, and which exhibit outstanding adhesionto mineral substrates. The preparation of such silanol group-containingvinyl eater polymers is the subject of DE-C-21 48 458 (GB-A-1 407 827),where it is taught to prepare the polymers by the emulsionpolymerization method with the organosilicon monomers being metered inin the course of polymerization, since otherwise, if the silane isincluded in the initial charge, the dispersion would contain coagulatesand lose its adhesion properties.

DE-A-38 03 450 (AU-A 89/29590) relates to low-emission polymerdispersions based on ethylenically unsaturated comonomers and from 0.05to 2% by weight of ethylenically unsaturated, hydrolyzable organosiliconcompounds. They are prepared by the emulsion polymerization method, withthe addition of the silicon monomer being a matter of open choice--itcan take place together with the comonomer phase or separately, duringthe entire duration of polymerization or with the first half and/or thesecond half of the comonomer phase.

DE-A-38 34 638 (U.S. Pat. No. 4,886,852) describes a highly complexmultistage process for the preparation of an aqueous dispersion. In afirst stage, a nonaqueous dispersion is prepared comprising 1 to 90% byweight of a vinyl monomer which contains alkoxysilane groups, 1 to 25%by weight of an α,β-ethylenically unsaturated carboxylic acid, and 9 to98% by weight of a further unsaturated monomer which can be polymerizedby a free-radical mechanism. In a second stage, at least one furtherfree-radically polymerizable monomer, in an organic solvent in which thepolymer particles formed are insoluble, is reacted in the presence ofthe dispersion stabilizing resin prepared in stage 1 to give a likewisenonaqueous dispersion. In a third stage, the neutralized nonaqueousdispersion is converted by addition of water into an aqueous dispersion.The dispersions prepared in accordance with this teaching are suitable,on the basis of their good water resistance, as coating compositions.

EP-A-35 332 describes the use of unsaturated organosilicon compounds forthe preparation of dispersions which are suitable as binders indispersion tile adhesives. In addition to the organosilicon compound,the copolymers also contain aromatic vinyl monomers and (meth) acrylatemonomers. They are prepared by including a portion of the monomer phasewith acrylic acid in the initial charge, and metering in the remainingportion with the entirety of organosilicon monomer.

EP-A-327 376 relates to a process for the preparation ofsilyl-containing copolymers of vinyl esters, if desired in a mixturewith further comonomers, such as acrylic esters, ethylene or vinylchloride, which have a low content of silane monomer and exhibit goodbinder properties. In the process, a portion of the silane is includedin the initial charge together with a portion of the other monomers, andthe remaining portion of the silane and of the monomers is metered in.The uniform distribution of the silane units in the polymer chain isregarded as being particularly advantageous.

EP-A-444 827 discloses a process for the emulsion polymerization ofcore/shell copolymers which comprise a core of vinylester/olefin/acrylate/vinylsilane copolymer and a vinyl ester/olefinshell. The initial charge in a polymerization comprises a portion of amixture of vinyl ester, acrylate and silane; ethylene is injected, andthe remaining portion of the comonomer mixture is metered in. Followingthe end of the metering of silane-containing monomer, a second,silane-free vinyl ester metering is commenced. This process brings aboutthe formation of a silane-containing hydrophobic core, which hasparticular strength because of crosslinking via the silane groups, andthe formation of a silane-free shell.

SUMMARY OF THE INVENTION

The object of the present invention was therefore to provide copolymerdispersions in which organosilicon comonomers are incorporated sofavorably into the copolymer that, even with small proportions oforganosilicon monomer, copolymer dispersions are obtained which havehigh-quality binder properties, such as water resistance, plasterhardness or abrasion resistance.

This object has been achieved by a procedure in which the unsaturatedorganosilicon component, together with a small quantity of predominantlyhydrophilic monomer, is reacted to give a water-swellable toalkali-soluble protective colloid which subsequently, in the course ofthe polymerization of the major proportion of the hydrophobic monomer inthe absence of further unsaturated organosilicon compounds, covers theresulting hydrophobic core as a shell layer. In this procedure, theorganosilicon compounds are incorporated into the copolymer so favorablythat it is possible, using unusually low quantities of organosiliconcompound, to obtain high-quality binder properties.

The invention provides core/shell copolymer dispersions having solidscontents of from 45 to 65% whose shell comprises hydrolyzableorganosilicon comonomers, the proportion of the shell in the core-shellcopolymer being from 2 to 25% by weight and the shell consisting of acopolymer comprising

a) from 70 to 95% by weight, based on the overall weight of the shell,of acrylic and/or methacrylic C₁ to C₁₀ alkyl esters of which from 20 to80% by weight, based on the overall weight of a), have awater-solubility of not more than 2 g/1 and from 80 to 20% by weight,based on the overall weight of a), have a water-solubility of at least10 g/l,

b) from 5 to 25% by weight, based on the overall weight of the shell, ofone or more ethylenically unsaturated, functional and water-solublemonomers including a proportion of from 25 to 100% by weight, based onthe overall weight of b), of unsaturated carboxylic acids, and

c) from 0.01 to 10% by weight, based on the overall weight of the shell,of one or more olefinically unsaturated, hydrolyzable silicon compoundsof the general formula R¹ --Si(OR²)₃ in which R¹ is an organic radicalwhich is olefinically unsaturated in the ω-position, and R², which isidentical or different at each occurrence, is a primary and/or secondaryalkyl or acyl radical which is optionally substituted with alkoxygroups,

and whose core, making up a proportion of from 75 to 98% by weight ofthe overall weight of the core/shell copolymer, consists of a polymercomprising

d) one or more comonomers from the group consisting of vinyl esters,acrylic and/or methacrylic esters, vinyl chloride, aromatic vinylcompounds and ethylene.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Suitable constituents of the mixture a) are the esters of acrylic and/ormethacrylic acid with straight-chain or branched aliphatic C₁ to C₁₀alcohols, in combination if desired with the corresponding diesters offumaric of maleic acid. A table relating to the water-solubility ofthese esters can be found in "Vinyl and Diene Monomers, Part 1", E. C.Leonard Ed., Wiley-Interscience, New York (1970) p. 149 ff.

Examples of suitable esters of acrylic, methacrylic, fumaric of maleicacid having a water-solubility of not more than 2 g/l are butylacrylate, ethylhexyl acrylate, ethyl methacrylate, butyl methacrylate,dibutyl maleate or fumarate and diethylhexyl maleate or fumarate. It ispreferred to use butyl acrylate and/or ethylhexyl acrylate.

Examples of suitable esters having a water-solubility of more than 10g/l are methyl acrylate, methyl methacrylate and ethyl acrylate.Particular preference is given to ethyl acrylate and/or methylmethacrylate.

Suitable constituents of the mixture b) are acrylic, methacrylic,itaconic, fumaric and/or maleic acid and the corresponding alkali metalsalts and ammonium salts; the mono- and, if appropriate, diamidesthereof, which may be substituted on the nitrogen by one or two methylolgroups; the monoesters of the above-mentioned dicarboxylic acids with C₁to C₃ alcohols; vinyl sulfonates, esters and/or amides of unsaturatedcarboxylic acids which are substituted with sulfonate groups, styreneswhich are substituted with sulfonate groups; N-vinylpyrrolidone,N-vinylformamide, and the hydroxyl-substituted esters of unsaturatedcarboxylic acids.

Preferred water-soluble monomers b) are acrylic acid, methacrylic acidand the alkali metal salts and ammonium salts thereof, acrylamide,methacrylamide, N-methylolacrylamide or -methacrylamide, vinylsulfonate, hydroxyethyl acrylate, and esters and/or amides of acrylic ormethacrylic acid which are substituted with sulfonate groups, an examplebeing sulfopropyl methacrylate. Particular preference is given toacrylic acid, methacrylic acid, acrylamide and methacrylamide.

Suitable olefinically unsaturated, hydrolyzable silicon compounds c) areγ-acryloyl- or γ-methacryloyl-oxypropyltri(alkoxy) silanes andvinyltrialkyoxysilanes, examples of the alkoxy groups which can beemployed being methoxy, ethoxy, methoxyethylene, ethoxyethylene,methoxypropylene glycol ether and ethoxypropylene glycol ether radicals.Another possibility for use is tris-acetoxyvinylsilane. Particularpreference is given to vinyltriethoxysilane,γ-methacryloyloxypropyltriethoxy-silane and trisacetoxyvinylsilane.

Examples of suitable free-radical polymerizable, unsaturated monomers d)are the branched or unbranched alkyl esters whose acid componentconsists of from 2 to 12 carbon atoms. Examples of component d) arevinyl acetate, vinyl propionate, vinyl pivalate, vinyl2-ethyl-hexanoate, VeoVa® 9 and VeoVa® 10 (vinyl esters of α-branchedcarboxylic acids having 9 to 10 carbon atoms). Other suitable monomersd) are the monoolefinically unsaturated mono- or dicarboxylic esterswhose acid component consists of 3 to 5 carbon atoms and whose alcoholcomponent consists of 1 to 8 carbon atoms, examples being acrylic and/ormethacrylic esters of methanol, ethanol, butanol and/or 2-ethylhexanol,such as methyl methacrylate, butyl acrylate and/or 2-ethylhexylacrylate.

The above-described monomers from the class of the unsaturated vinylesters and of the monoolefinically unsaturated mono- or dicarboxylicesters may if desired be employed in combination with vinyl chlorideand/or ethylene.

Other suitable monomers d) are aromatic vinyl compounds, preferablystyrene in combination with monomers from the group of themonoolefinically unsaturated mono- or dicarboxylic esters. In smallquantities it is also possible to employ polyethylenically unsaturatedmonomers such as allyl methacrylate, divinyl adipate, butanedioldiacrylate and triallyl cyanurate, in quantities of from 0 to 2% byweight, preferably from 0.05 to 0.5% by weight, based in each case onthe overall weight of the monomers d).

The monomers d) employed are preferably vinyl acetate, VeoVa® 9, VeoVa®10 trademarks of the Shell Oil Company for vinyl esters of a syntheticsaturated monocarboxylic acid mixture of highly branched C₉ and C₁₀isomers, methyl methacrylate, butyl acrylate, 2-ethylhexyl acrylate,vinyl chloride, ethylene and/or styrene.

The core/shell copolymer preferably comprises: from 5 to 15% by weightof a shell copolymer comprising

a) from 80 to 95% by weight, based on the overall weight of the shell,of comonomer a), of which from 40 to 60% by weight comprises butylacrylate and/or ethylhexyl acrylate and from 60 to 40% by weight, basedin each case on the overall weight of the comonomers a), comprises ethylacrylate, methyl acrylate and/or methyl methacrylate,

b) from 5 to 15% by weight, based on the overall weight of the shell, ofacrylic acid and/or methacrylic acid, together if desired withacrylamide and/or methacrylamide,

c) from 0.5 to 10% by weight, based on the overall weight of the shell,of vinyltriethoxysilane, γ-methacryloyloxypropyltriethoxysilane and/ortris-acetoxyvinylsilane, and

from 75 to 95% by weight of a core copolymer based on vinylchloride-ethylene, vinyl chloride-ethylene-vinyl acetate, vinylchloride-ethylene-VeoVa9 and/or VeoVa10, vinyl acetate-ethylene, vinylacetate-VeoVa9 and/or VeoVa10, methyl methacrylate-butyl acrylate,methyl methacrylate-2-ethylhexyl acrylate, methyl methacrylate-butylacrylate-VeoVa9 and/or VeoVa10, styrene-butyl acrylate, styrene-butylacrylate-VeoVa9 and/or VeoVa10, styrene-2-ethylhexyl acrylate-VeoVa9and/or VeoVa10 or styrene-2-ethylhexyl acrylate copolymers.

Particularly preferred core copolymers are vinyl chloride copolymerswith an ethylene content of from 5 to by weight which may if desiredalso contain from 1 to by weight of vinyl acetate, VeoVa9 and/orVeoVa10; vinyl acetate copolymers containing from 5 to 25% by weight ofethylene and/or from 1 to 40% by weight of VeoVa9 and/or VeoCa10, methylmethacrylate copolymers containing from 30 to 60% by weight of butylacrylate or 2-ethylhexyl acrylate, which may if desired also containfrom 1 to 20% by weight of VeoVa9 and/or VeoVa10; and styrene copolymerscontaining from 30 to 60% by weight of butyl acrylate or 2-ethylhexylacrylate, which may if desired also contain from 1 to 20% by weight ofVeoVa9 and/or VeoVa10.

The invention additionally provides a process for the preparation ofcopolymer dispersions comprising hydrolyzable organosilicon comonomersand having solids contents of from 45 to 65% by free-radical emulsionpolymerization of from 2 to 25% by weight, based on the overall weightof the comonomers a), b), c) and d), of a comonomer mixture comprising

a) from 70 to 95% by weight, based on the overall weight of comonomersa), b) and c), of acrylic and/or methacrylic C₁ to C₁₀ alkyl esters ofwhich from 20 to 80% by weight, based in each case on the comonomers a),have a water-solubility of at least 10 g/l, with

b) from 5 to 25% by weight, based on the overall weight of comonomersa), b) and c) of one or more ethylenically unsaturated, functional andwater-soluble monomers including a proportion of from 25 to 100% byweight, based on the comonomers b), of unsaturated carboxylic acids, and

c) from 0.01 to 10% by weight, based on the overall weight of comonomersa), b) and c), of one or more olefinically unsaturated, hydrolyzablesilicon compounds of the general formula R¹ --Si(OR²)₃ in which R¹ is anorganic radical which is olefinically unsaturated in the ω-position, andR², which is identical or different at each occurrence, is a primaryand/or secondary alkyl or acyl radical which is optionally substitutedwith alkoxy groups,

in which the constituents mentioned under a), b) and c), together withwater and emulsifier, are initially charged to a reactor at a pH of from2 to 5, polymerization is begun at a temperature of from 40 to 90° C. byadding an initiator,

and, at a degree of conversion of at least150% of the monomers mentionedunder a), b) and c), the metered addition is begun of from 75 to 98% byweight, based on the overall weight of the comonomers a), b), c) and d),of one or more further olefinically unsaturated monomers

d) from the group consisting of vinyl esters, acrylic and/or methacrylicesters, vinyl chloride, aromatic vinyl compounds and ethylene, andfurther emulsifier and/or initiator.

The process can be carried out such that the polymerization of themonomers mentioned under d) together with the required emulsifier and/orinitiator is either carried out directly following the preparation ofthe alkali-soluble protective colloid of the first stage, i.e. directlyafter the end of the metered addition of the comonomer mixturecomprising a), b) and c), or is carried out subsequently in a separatestage.

Suitable emulsifiers are nonionic and/or anionic surfactants such as,for example:

1) Alkyl sulfates, especially those having a chain length of from 8 to18 carbon atoms, alkyl and alkylaryl ether sulfates having 8 to 18carbon atoms in the hydrophobic radical and 1 to 50 ethylene oxideunits.

2) Sulfonates, especially alkylsulfonates having 8 to 18 carbon atoms,alkylarylsulfonates having 8 to 18 carbon atoms, esters and half-estersof sulfosuccinic acid with monohydric alcohols or alkylphenols having 4to 15 carbon atoms in the alkyl radical; if desired, these alcohols oralkylphenols may also be ethoxylated with from 1 to 40 ethylene oxideunits.

3) Partial esters of phosphoric acid, and the alkali metal salts andammonium salts thereof, especially alkyl and alkylaryl phosphates having8 to 20 carbon atoms in the organic radical, alkyl ether and alkylarylether phosphates having 8 to 20 carbon atoms in the alkyl or alkylarylradical and 1 to 50 EO units.

4) Alkyl polyglycol ethers, preferably with 8 to 40 EO units and alkylradicals of 8 to 20 carbon atoms.

5) Alkylaryl polyglycol ethers, preferably with 8 to 40 EO units and 8to 20 carbon atoms in the alkyl and aryl radicals.

6) Ethylene oxide-propylene oxide (EO-PO) block copolymers, preferablywith 8 to 40 EO and PO units.

Preferred anionic emulsifiers in the polymerization of the mixturecomprising a), b) and c) are the representatives of groups 1 and 2having less than 10 ethylene oxide units; emulsifiers which are free ofethylene oxide groups are particularly preferred. For the addition ofthe monomers d), preferred emulsifiers are the ethoxylatedrepresentatives of groups 1 to 5. Particular preference is given to theethoxylated representatives of group 1.

The polymerization is initiated by the methods which are usuallyemployed. Inorganic or organic peroxidic compounds which are at leastpartially water-soluble, preferably completely water-soluble, such asperoxo compounds, hydroperoxides and per esters, and water-soluble azocompounds, are particularly suitable. Among those which may be mentionedare alkali metal or ammonium peroxo(di)sulfates or -phosphates, hydrogenperoxide, tert-butyl hydroperoxide, azobiscyanovaleric acid andtert-butyl permaleate. The abovementioned peroxides may also, ifdesired, be combined in the known manner with reducing agents. Examplesof suitable reducing agents are alkali metal formaldehyde sulfoxylates(BRUOGGOLIT®, RONGALIT®), alkali metal sulfites and bi-sulfites, alkalimetal thiosulfates and ascorbic acid. In a known manner, in many casesthe use of small quantities of heavy metal salts then becomesappropriate, examples being iron(II) salts. Thermal polymerization usingalkali metal or ammonium peroxo(di)sulfates is particularly preferred.Preference is given to the use of a quantity of initiator of from 0.01to 1.0% by weight, based on the overall weight of the comonomers.

It is possible to employ further conventional auxiliaries, such asbuffer substances, regulators or inhibitors which prevent prematurepolymerization.

In the text below, a particularly preferred embodiment of the process isdescribed in more detail:

The monomers mentioned under b) are introduced as initial chargetogether with deionized water, from 0.5 to 10 parts, preferably from 1to 5 parts, by weight of a preferably anionic emulsifier or emulsifiermixture, and, if desired, further conventional additives such asbuffers, regulators and inhibitors, and a pH of from 2 to 5, preferablyfrom 2.5 to 4, is established by adding preferably volatile acids orbases such as, for example, formic acid or ammonia. Following additionof the monomers mentioned under a) and c) and the establishment of thepolymerization temperature of from 40° to 90° C., preferably from 60° to80° C., the polymerization is begun by adding an initiator.

As soon as the monomers mentioned under a) to c) have reacted to theextent of from 40 to 99%, preferably from 50 to 95%, the meteredaddition of the monomers mentioned under d), of the remaining amount ofemulsifier and the remaining amount of water in the form of apreemulsion is commenced; if desired, ethylene is injected. In the casewhere ethylene is copolymerized, the ethylene pressure is preferablymaintained at a constant level during the polymerization of from 40 to80 bar, preferably from 50 to 70 bar, and is allowed to drop toward theend of polymerization by shutting off the supply of ethylene.

After the end of the addition of the constituents d), the supply ofinitiator is maintained until the monomers employed, except for anyethylene used, have reacted to the extent of more than 98%, preferablymore than 99%. The pH of the dispersion is then adjusted to valuesbetween 6 and 10, preferably between 7 and 9, any overpressure stillpresent is released, and the dispersion is degassed by applying avacuum, stripped if desired in a manner known per se and then cooled.

In particular, in the case of the copolymerization of ethylene into thecore polymer, from 1 to 10% by weight of the monomers d) are initiallyintroduced together with the monomers a), b) and c) as a swelling agentwhich cannot, or not to any great extent, be copolymerized with thecomonomers a), b) and c). For this purpose, the comonomers d) employedcan only be those which under the conditions of the polymerization ofthe shell polymer do not, or not to any great extent, undergocopolymerization with the monomers a), b) or c). Such monomers are vinylacetate and vinyl esters of carboxylic acids having 5 to 10 carbonatoms, such as vinyl pivalate, vinyl ethylhexanoate, VeoVa® 9, VeoVa®10.

The dispersions according to the invention are suitable for theproduction of polymer-bound plasters having good water resistance,complete heat insulation systems, and interior and exterior paintshaving good abrasion resistance. In addition, the dispersions areparticularly suitable for the production of water-resistant dispersiontile adhesives.

The examples which follow serve to illustrate the invention in moredetail.

A) Preparation of the Starting Dispersions EXAMPLE 1

4120 ml of deionized water, 260 g of a 15% strength by weight aqueoussodium alkylbenzenesulfonate solution, 130 g of a 30% strength by weightaqueous acrylamide solution and 81 g of methacrylic acid were placed ina stirrer autoclave with a capacity of about 16 l. The pH was adjustedto 3.5 with dilute NH₃. The autoclave was then evacuated, flushed withnitrogen and evacuated again, and a mixture of 400 g of butyl acrylate,400 g of methyl methacrylate, 340 g of VeoVa® 10 and 23 g ofmethacryloyloxypropyltrimethoxysilane (Silan GF 31, Wacker-Chemie GmbH)was introduced under suction. This mixture was stabilized againstpremature polymerization by the addition of 170 mg of benzoquinone.After heating to 70° C., 100 ml of 20% strength by weight aqueousammonium persulfate solution were added over the course of 3 minutes. 20minutes later, the initial monomer charge had reacted to the extent of55%. At this point in time, 65 bar of ethylene were injected. At thesame time, the metered addition of 20% strength by weight aqueousammonium persulfate solution was begun at a rate of 60 ml/h, as was thatof a preemulsion comprising 2780 g of water, 960 g of a 35% strength byweight aqueous solution of a nonylphenol polyethylene oxide sulfatecontaining about 25 mol of ethylene oxide per mole of emulsifier, and6540 g of vinyl chloride. During this period, the pH was maintained atbetween 5 and 6 by adding NH₃ and the ethylene pressure was maintainedat 65 bar.

After the end of the metered addition of pre-emulsion, the metering ofethylene and initiator was stopped and the contents of the reactor weremaintained at 70° C. for one hour. After adjustment of the pH to 8.5 byaddition of ammonia, ethylene was blown off and the dispersion wasstirred in a vacuum for one hour.

Analysis revealed an ethylene content of about 15%, a solids content of47.9% and a viscosity (Brookfield viscometer, 20° C., 20 rpm) of 700mPa.s. The product showed a minimum film-forming temperature of 25° C.

EXAMPLE 2

In the formulation of Example 1, 53.5 g ofmethacryloyloxypropyltrimethoxysilane were employed in the preparationof the first stage. A dispersion having a solids content of 51.1% and aviscosity of 100 mPa.s was obtained. The dispersion showed a minimumfilm-forming temperature of 25° C.

EXAMPLE 3

In the formulation of Example 1, in the preparation of the first stagethe methacryloyloxypropyltrimethoxysilane was replaced by 77 g ofvinyltriethoxysilane (Silan GF 56, Wacker Chemie GmbH). A 49.8% strengthdispersion was obtained which had a viscosity of 140 mPa.s. The minimumfilm-forming temperature was 31° C.

EXAMPLE 4

66 g of butyl acrylate, 66 g of methyl methacrylate, 55 g of VeoVa®10,6.3 g of methacryloyloxypropyltrimethoxysilane, 21.9 g of a 30% strengthby weight acrylamide solution, 13.2 g of methacrylic acid and 43.7 g ofa 15% strength by weight solution of an alkylsulfonate in 520 ml ofwater were initially charged to a 2.4 l laboratory autoclave; ethylenewas not injected. The reaction was initiated by addition of ammoniumpersulfate at 71° C. At a solids content of 17%, an emulsion of 537 g ofmethyl methacrylate, 537 g of butyl acrylate, 159 g of a 35% strength byweight solution of a sulfated nonylphenol ethoxylate containing about 25EO units in 458 g of water was added. A dispersion was obtained with asolids content of 52.8% and a viscosity of 2000 mPa.s; the minimumfilm-forming temperature was 12° C.

EXAMPLE 5

The formulation of Example 4 was altered in the following respects:

In the monomer feed, a mixture of 524 g of styrene and 524 g of butylacrylate was used instead of methyl methacrylate/butyl acrylate. A 51.8%strength dispersion was obtained which had a viscosity of 6500 mPa.s;the minimum film-forming temperature was 13° C.

EXAMPLE 6

The formulation of Example 1 was altered in the following respects:

In the initial monomer charge, 15 g ofmethacryloyloxypropyltrimethoxysilane were employed. In the monomerfeed, an additional 340 g of VeoVa®10 were used, and the quantity ofwater was increased correspondingly. A 52.3% strength dispersion wasobtained which had a viscosity of 3180 mPa.s; the minimum film-formingtemperature was 24° C.

EXAMPLE 7

The formulation of Example 4 was altered in the following respects:

In the monomer feed, a mixture of 322 g of VeoVa®9 and 749 g of vinylacetate was used instead of methyl methacrylate/butyl acrylate. A 52.3%strength dispersion was obtained which had a viscosity of 490 mPa.s; theminimum film-forming temperature was 25° C.

COMPARISON EXAMPLE 1

The formulation of Example 1 was altered in that, during thepreparation, no methacryloxypropyltrimethoxysilane was employed in theinitial monomer charge. A dispersion was obtained which had a solidscontent of 52% at a viscosity of 2500 mPa.s; the minimum film-formingtemperature was 19° C.

COMPARISON EXAMPLE 2

The formulation of Example 1 was altered in that, in the initial monomercharge, only butyl acrylate was used instead of the mixture of methylmethacrylate and buryl acrylate. The batch coagulated at the blowing-offstage.

COMPARISON EXAMPLE 3

The formulation of Example 4 was altered in that, in the course ofpreparation, no methacryloyloxypropyltrimethoxysilane was used in theinitial monomer charge. A dispersion was obtained which had a solidscontent of 52.7% at a viscosity of 7050 mPa.s. The minimum film-formingtemperature was 13° C.

COMPARISON EXAMPLE 4

The formulation of Example 5 was altered in that nomethacryloyloxypropyltrimethoxysilane was used in the initial monomercharge. A dispersion was obtained which had a solids content of 52% anda viscosity of 11,800 mPa.s. The minimum film-forming temperature was14° C.

COMPARISON EXAMPLE 5

The formulation of Example 7 was altered in that nomethacryloyloxylpropyltrimethoxysilane was used in the initial monomercharge. A dispersion was obtained which had a solids content of 52.2%and a viscosity of 1325 mPa.s. The minimum film-forming temperature was26° C.

COMPARISON EXAMPLE 6

The formulation of Example 1 was altered in that nomethacryloyloxypropyltrimethoxysilane was used in the initial monomercharge; 77 g of vinyltriethoxysilane were used in the feed. A dispersionwas obtained which had a solids content of 49.3% and a viscosity of 1360mPa.s.

B) Applications-Related Testing

The dispersions from the examples or comparison examples were tested ina formulation for tile adhesives and in a formulation for plasters.

Test formulation for dispersion tile adhesives:

    ______________________________________                                        parts      substance                                                          ______________________________________                                        0.20       water                                                              0.10       preservative (Parmetol DF 12)                                      0.15       dispersant (Styrodex PK 90)                                        0.20       thickener (Tylose MHP 30000yp)                                     0.25       thickener (Rohagit SD 15)                                          0.05       dispersion auxiliary (AMP 90)                                      0.15       ammonia                                                            0.15       defoamer (Agitan 281)                                              51.80      CaCO.sub.3 filler (Durcal 40)                                      8.50       CaCO.sub.3 filler (Durcal 10)                                      37.75      dispersion (solids content 50% by weight)                          ______________________________________                                    

The adhesives of the above formulation were adjusted using plasticizer(1:1 mixture of Dowanol DPnB and Dowanol PnB) to a minimum film-formingtemperature of 0° C.

The adhesives of the above formulation were used to stick ceramic tilesonto concrete, and the tensile adhesion strength of the bonded tilesafter different storage cycles was tested in accordance with DIN 18156.The test results are compiled in Table 1:

                  TABLE 1                                                         ______________________________________                                        Tensile adhesive strength  N/mm.sup.2)                                                    28 days     28 days normal climatic                                           normal climatic                                                                           conditions/21 days                                    Sample      conditions  storage in water                                      ______________________________________                                        Example 1   1.40        0.71                                                  Example 2   1.57        0.74                                                  Example 3   1.74        0.67                                                  Example 4   1.21        0.32                                                  Example 5   1.29        0.45                                                  Example 6   1.84        0.59                                                  Example 7   1.72        0.38                                                  Comp. Ex. 1 1.35        0.14                                                  Comp. Ex. 3 1.30        <0.10                                                 Comp. Ex. 4 1.38        0.12                                                  Comp. Ex. 5 1.79        <0.10                                                 Comp. Ex. 6 1.53        0.12                                                  ______________________________________                                    

Test formulation for plasters:

    ______________________________________                                        parts      substance                                                          ______________________________________                                        2.50       preservative (Parmetol DF 12)                                      2.50       defoamer (Bevaloid 677)                                            32.0       cellulose thickener (Walcocel MW 3000 GB 3%                                   strength)                                                          0.10       wetting agent (Calgon N dry)                                       30.0       titanium dioxide (RN 56)                                           150.0      mica filler (Plastorit 0.5)                                        30.0       dolomite filler (Microdol 820)                                     150.0      heavy spar filler (Fleur)                                          100.0      ground quartz (W 4)                                                140.0      crystalline quartz sand (No. 8a)                                   50.0       crystalline quartz sand (No. 4 extra)                              150.0      dispersion (solids content 50% by weight)                          ______________________________________                                    

The abovementioned formulations were adjusted to a minimum film-formingtemperature of 0° C. with from 3.0 to 6.5 parts of butyl diglycolacetate, and for the preparation of the plasters were made up to 1000parts with water.

In order to determine the plaster softening, the penetration depth inaccordance with Buchholz (DIN 53153) was determined, and the values from5 measurements were averaged.

The plaster adhesion was determined manually with a spatula, and given aqualitative rating ranging from 1 to 6 with decreasing adhesion. Theresults are compiled in Table 2.

                  TABLE 2                                                         ______________________________________                                                     Plaster softening                                                                         Plaster adhesion                                     Sample        mm!        rating                                               ______________________________________                                        Example 1    3.5         2.5                                                  Example 2    3.0         2.5                                                  Example 4    4.5         2.0                                                  Example 5    4.5         2.0                                                  Example 7    2.5         1.0                                                  Comparison Ex. 1                                                                           4.5         3.5                                                  Comparison Ex. 3                                                                           4.5         4.0                                                  Comparison Ex. 4                                                                           5.5         5.0                                                  Comparison Ex. 5                                                                           4.5         3.0                                                  Comparison Ex. 6                                                                           4.5         3.0                                                  ______________________________________                                    

Testing of water uptake:

The dispersions were drawn onto a polypropylene sheet in a wet filmthickness of 500 μm and were dried at room temperature. After detachingthe film from the sheet, specimens measuring 5×5 cm were punched out andtheir dry weight was determined. The specimens were stored in distilledwater for 1 and/or 21 days and then gently dried with a paper towel. Theuptake of water, based on the initial weight of the specimen, wasdetermined by weighing; the increase in % by weight is listed in Table3.

                  TABLE 3                                                         ______________________________________                                                     Water uptake                                                                              Water uptake after                                   Sample       after 1 day  %!                                                                           21 days  %!                                          ______________________________________                                        Example 1    12          17                                                   Example 2    7           3                                                    Example 4    21          16                                                   Example 5    19          15                                                   Example 7    47          63                                                   Comparison Ex. 1                                                                           12          82                                                   Comparison Ex. 3                                                                           42          70                                                   Comparison Ex. 4                                                                           24          111                                                  Comparison Ex. 5                                                                           60          112                                                  Comparison Ex. 6                                                                           19          45                                                   ______________________________________                                    

We claim:
 1. A core/shell copolymer dispersion having a solid content offrom 45 to 65% whose shell comprises hydrolyzable organosiliconcomonomers, the proportion of the shell in the core-shell copolymerbeing from 2 to 25% by weight and the shell comprised of a copolymerconsisting essentially of a) at least 70% by weight, based on theoverall weight of the shell, of acrylic and/or methacrylic C₁ to C₁₀alkyl esters of which from 20 to 80% by weight, based on the overallweight of a), have a water-solubility of not more than 2 g/l and from 80to 20% by weight, based on the overall weight of a), have awater-solubility of at least 10 g/l, b) from 5 to 25% by weight, basedon the overall weight of the shell, of one or more ethylenicallyunsaturated, functional and water-soluble monomers and wherein (b) iscomprised of by weight, at least 25% and up to and including 100% ofunsaturated carboxylic acids, and c) from 0.01 to 10% by weight, basedon the overall weight of the shell, of one or more olefinicallyunsaturated, hydrolyzable silicon compounds of the general formula R¹--Si (OR²)₃ in which R¹ is an organic radical which is olefinicallyunsaturated in the ω-position, and R², which is identical or differentat each occurrence, is a primary and/or secondary alkyl or acyl radicalwhich is optionally substituted with alkoxy groups, and whose core,makes up a proportion of from 75 to 98% by weight of the overall weightof the core/shell copolymer, comprised of a polymer consistingessentially of d) one or more comonomers from the group consisting ofvinyl esters, acrylic and/or methacrylic esters, vinyl chloride,aromatic vinyl compounds and ethylene.
 2. A core/shell copolymerdispersion as claimed in claim 1, wherein the core/shell copolymercomprises from 5 to 15% by weight of a shell copolymer comprisinga) atleast 80% by weight, based on the overall weight of the shell, ofcomonomer a), of which from 40 to 60% by weight comprises butyl acrylateand/or ethylhexyl acrylate and from 60 to 40% by weight, based in eachcase on the overall weight of the comonomers a), comprises ethylacrylate and/or methyl methylacrylate, b) from 5 to 15% by weight, basedon the overall weight of the shell, of acrylic acid and/or methacrylicacid, optionally with acrylamide and/or methacrylamide, c) from 0.5 to10% by weight, based on the overall weight of the shell, ofvinyltriethoxysilane, γ-methacryloyloxypropyltriethoxysilane and/ortrisacetoxyvinylsilane.
 3. A core/shell copolymer dispersion as claimedin claim 1, wherein the core-shell copolymer comprises from 75 to 95% byweight of a core copolymer based on vinyl chloride-ethylene copolymers,vinyl chloride-ethylene-vinyl acetate copolymers, copolymers of vinylchloride and ethylene with vinyl esters of α-branched carboxylic acidshaving 9 and/or 10 carbon atoms, vinyl acetate-ethylene copolymers,copolymers of vinyl acetate with vinyl esters of α-branched carboxylicacids having 9 and/or 10 carbon atoms, methylmethacrylate-butyl-acrylate copolymers, methyl methacrylate-2-ethylhexylacrylate copolymers, copolymers of methyl methacrylate and butylacrylate with vinyl esters of α-branched carboxylic acids having 9and/or 10 carbon atoms, styrene-butyl acrylate copolymers,styrene-2-ethylhexyl acrylate copolymers, copolymers of styrene andbutyl acrylate with vinyl esters of a-branched carboxylic acids having 9and/or 10 carbon atoms, or copolymers of styrene and 2-ethylhexylacrylate with vinyl esters of α-branched carboxylic acids having9-and/or 10 carbon atoms.
 4. A process for the preparation of core/shellcopolymer dispersions as claimed in claim 1 by free-radical emulsionpolymerization of from 2 to 25% by weight, based on the overall weightof comonomers a), b), c) and d), of a comonomer mixture comprisinga) atleast 70% by weight, based on the overall weight of the comonomers a),b) and c), of acrylic and/or methacrylic C₁ to C₁₀ alkyl esters of whichfrom 20 to 80% by weight have a water-solubility of not more than 2 g/land from 80 to 20% by weight, based in each case on the monomers a),have a water-solubility of at least 10 g/l, with b) from 5 to 25% byweight, based on the overall weight of the comonomers a), b) and c), ofone or more ethylenically unsaturated, functional and water-solublemonomers and wherein (b) is comprised of by weight, at least 25% and upto 100% of unsaturated carboxylic acids, and c) from 0.01 to 10% byweight, based on the overall weight of the comonomers a), b) and c), ofone or more olefinically unsaturated, hydrolyzable silicon compounds ofthe general formula R¹ --Si (OR²)₃ in which R¹ is an organic radicalwhich is olefinically unsaturated in the ω-position, and R², which isidentical or different at each occurrence, is a primary and/or secondaryalkyl or acyl radical which is optionally substituted with alkoxygroups, in which the constituents mentioned under a), b) and c),together with water and emulsifier, are initially charged to a reactorat a pH of from 2 to 5, polymerization is begun at a temperature of from40° to 90° C. by adding an initiator, and, at a degree of conversion ofat least 50% of the monomers mentioned under a), b) and c), the meteredaddition is begun of from 75 to 98% by weight, based on the overallweight of the comonomers a), b) c) and d), of one or more furtherolefinically unsaturated monomers d) from the group consisting of vinylesters, acrylic and/or methacrylic esters, vinyl chloride, aromaticvinyl compounds and ethylene, and further emulsifier and/or initiator.5. The process as claimed in claim 4, wherein the monomers mentionedunder b) are introduced as initial charge together with deionized water,from 0.5 to 10 parts by weight of a preferably anionic emulsifier oremulsifier mixture, and a pH of from 2 to 5, is established, afteraddition of the monomers mentioned under a) and c) and the establishmentof the polymerization temperature of from 40° to 90° C., thepolymerization is begun by adding an initiator, and as soon as themonomers mentioned under a) to c) have reacted to the extent of from 40to 99%, the metered addition of the monomers mentioned under d), of theremaining amount of emulsifier and the remaining amount of water in theform of a preemulsion is commenced, and after the end of the addition ofthe constituents d), the supply of initiator is maintained until themonomers employed, except for any ethylene used, have reacted to theextent of more than 98%.
 6. The process as claimed in claim 4, wherein,in the case of the copolymerization of ethylene into the core polymer,from 1 to 10% by weight of the monomers d) are initially introducedtogether with the monomers a), b) and c) as a swelling agent, in whichcontext the comonomers d) employed can only be those which lender theconditions of the polymerization of the shell polymer do not, or not toany great extent, undergo copolymerization with the monomers a), b) orc).
 7. A polymer-bound plaster containing as a binder the core/shellcopolymer dispersion of claim
 1. 8. A heat insulating system containingas a binder the core/shell copolymer dispersion of claim
 1. 9. Aninterior and exterior paint containing as a binder the core/shellcopolymer dispersion of claim
 1. 10. A tile adhesive containing as abinder the core/shell copolymer dispersion of claim 1.